Light sources based on light-emitting diodes (LEDs) have matured within a few years to become a competitive alternative to traditional light sources, such as incandescent lamps, halogen lamps or (compact) fluorescent lamps, for example. LED technology has advanced to provide a greater efficiency than fluorescent lamps. Consequently, LED lighting solutions have increasingly gained entry into areas in which fluorescent lamps previously dominated. Many fluorescent lamp applications are concentrated in the professional field (office), because light control installations incorporated in an automated building system (e.g. LON, EIB) are often in use here.
Installations of that kind are projected on a predetermined period of use, as a result of which conversion to energy-saving LED lighting technology results in a substantial outlay for re-equipment. Consequently, LED lamps are constructed as a direct replacement for fluorescent lamps to retrofit the existing fittings. These so-called retrofit lamps are available on the market as double-end LED lamps with the respective standard G13 socket (T8 lamps with 26 mm tube diameter) or G5 socket (T5 lamps with 16 mm tube diameter).
When defective fluorescent lamps are replaced, particularly in the case of double-end fluorescent lamps, it is usual practice to replace the lamp without previously switching the fitting to be free of voltage. Moreover, there is even a method to identify a light in an existing light fitting relative to a control device in that the corresponding light source is rotated out of the mount during operation, so-called ‘relamping.’ Electronic ballast units for low-pressure discharge lamps, particularly fluorescent lamps, are constructed in such a way that for the case of a lamp inserted only at one end in a socket supplied with voltage the possibility of an electric shock for anyone holding the lamp is excluded. In that case, fluorescent lamps may include a gas content of the interior of the tube that is highly resistive in a non-ignited state, i.e. insulating. As a consequence, an exposed end of a fluorescent lamp can be held without concern while the other end has a voltage potential.
This inherent protective characteristic is not present at the outset in the case of LED lamps. However, safety standard IEC 62776 requires that double-end lamps not have a voltage at the opposite end at the time of mounting the lamp with a socket fitted at one end to avoid risk of an electric shock. In this connection, DE 10 2011 100 285 A1 discloses devices for safety connection against electric shock and destruction for double-end light sources such as LED tubes and fluorescent tubes. To avoid electrical intrusion into the light, a respective pushbutton as a closer is installed in the two end caps of the tube. The positioning of the button between the contacts to suit all socket types is critical. The button closes when fitting the contact to the electrical terminals, and an open current-conducting end is effectively prevented. Through installation of contacts in the LED tube, a current flow is possible only when the tube is correctly inserted and locked.